|Winter is a difficult time for insects|
Winter is quite a difficult time for pollinators. It is cold and often rainy and the first frosts will wipe out most of the flowers, and thus drastically reduce the availability of food. Pollinators have evolved various strategies to overcome this problem. In the following, we describe some of these strategies.
Bumblebees, at least from our perspective, have evolved quite a radical way to deal with the problem. The whole colony including the workers and the old queen die before winter and only the young queens reared in the colony will survive to start new colonies in the following spring. In autumn, they drink a huge amount of nectar to fill their honey stomach and to build up body fat and then they go searching for a suitable hiding place for hibernation. These hiding places are mostly underground, under tree roots and hedgerows or at the base of walls. If the young queens have not reached a certain weight before the onset of winter they are likely not to survive winter. Therefore it is really important they find enough nectar-rich flowers in autumn such as Cosmos (Cosmos spp.), Michaelmas daisies (Aster spp.) and single-flowered Dahlias (Dahlia x hybrida).
In spring, the queens emerge from hibernation and feed on
early flowers such as soft fruit blossom (e.g. Gooseberry and Black currant), early flowering fruit trees, Lesser celandine (Ficaria verna), Dandelion (Taraxacum sp.) and spring bulbs (e.g. Crocus) before starting to build new colonies.
The earliest queens to emerge are those of the Buff-tailed Bumblebee (Bombus terrestris), and you can usually see
them searching for flowers on the first warm days in March. They are quite big
and often a bit clumsy after their long hibernation, and thus easy to spot. The
aptly named Early Bumblebee (Bombus
pratorum) is the earliest among the UK’s bumblebee species to establish
colonies and the first worker bumblebees you see flying in spring are likely to
be of this species.
|Bumblebee queens need to drink a lot of nectar in autumn|
|A Buff-tailed Bumblebee queen searching for nectar|
|Winter-active Buff-tailed Bumblebee collecting pollen in January|
Solitary bees do not maintain colonies and have neither queens nor workers, and therefore they have evolved different strategies to survive winter. Adult bees are normally active for only about 3 month in the year (mostly spring/summer depending on the species) and then die after the business of mating and nest building is finished. The offspring survives winter either as young adults (most of the early-emerging bee species), as pupae (many of the later-emerging bees) or as larvae (usually found among species emerging very late) inside the nest cells which, depending on the exact species, have been built in hollow reeds, in holes in wood or walls, in dead stems or in underground chambers.
|Solitary bees have evolved different strategies to survive winter|
|Red mason bee emerging from nesting chamber in spring|
|Mason Bee nesting chambers (closed with mud) in cardboard tubes|
|Ivy bee emerging from an underground nest|
|Honeybees stop foraging if temperature falls below 10 °C|
|This Eristalis sp. hoverfly has overwintered as an adult|
|Hoverfly enjoying the last warm days in autumn|
Butterflies and moths display a wide range of strategies to survive winter. Depending on the species, they can overwinter as egg, as caterpillar (= the larva of moths and butterflies), as chrysalis (= the pupa of moths and butterflies), as hibernating imago (= the adult moth or butterfly), as active imago, or by migration to warmer climates.
|Butterflies and moth survive winter in many different ways|
|Meadow Brown butterflies overwinter as caterpillars|
|This Small copper has overwintered as caterpillar|
By contrast, hawk moths overwinter as pupae and spend winter in warm cocoons underground. Orange Tip, Holly Blue and Large and Small White butterflies (with the latter two species sometimes referred to as ‘Cabbage Whites’) are examples of butterflies overwintering as pupae.
|Hawk moth caterpillars look for suitable overwintering sites in late summer|
|Small Tortoiseshell`s hibernate in sheltered places|
In a minority of moth and butterfly species, the adults remain active during winter. These species have evolved the capability to produce an anti-freezing agent which stops ice-crystals forming in their ‘blood’ if temperatures are below 0 °C (without such an anti-freezing agent, exposure to subzero temperatures is a sure way to kill an insect). Examples of such species include the aptly named Winter Moth, which is active between November and February and which is a pest of fruit trees and the December Moth which you can encounter even on very cold days, usually in November and December.
|Painted Ladies migrate back to Africa before winter sets in|
|Many Red admiral`s migrate back to continental Europe|
We hope you enjoyed reading about the ingenious ways of pollinators to survive our winters. Look out in spring for the lucky ones, the pollinators which have survived winter, and celebrate a new year of bees, butterflies, hoverflies and other pollinators buzzing and busily flying around our flowers and crops.
Long may it continue ... .